Features are functionalities of communication terminals. There are service-independent features with additional functions, which facilitate and simplify the operation of a communication terminal. Features can also be based on service features. In the case of telephones, open listening, last number redial, handsfree talking, release, transfer, last number redial, automatic callback or call forwarding are examples of such features.
When communication installations are networked within a communication system, the number of features available system-wide has up to now been determined on the one hand by the fact that the features have to be available in the communication installations in question. On the other hand it must be possible to transmit items of feature control information using a system standard signaling protocol. Therefore the number of features available system-wide has up to now been very small compared with the number of features available in one of the communication installations.